Abstract
Dear Editor,
O’Brien et al. recently evaluated the accuracy of various methods of measuring patient height to establish ideal body weight and thus tidal volume for ventilation. 1 They reported that the 2 m tape was the most accurate method with a mean tidal volume exactly the same as that derived from standing height. However, other methods were also reasonably accurate, mainly under-predicting tidal volume by 20 mL on average. Standard deviations of all techniques overlapped substantially indicating that with the small sample size of the study, no statistical conclusions could be drawn on the relative accuracy of the methods.
We recently implemented a new ulnar ruler in our 16-bedded ICU using a quality improvement approach. Having initially started the project with a 2 m tape, we found poor reliability and repeatability difficulties with it. Our ulnar ruler doubles as a poster in every bed space displaying the patient name, ideal body weight and tidal volume for 6 mL/kg (all of which are read directly from the ruler when measuring ulnar length). Since implementing the technique last February, we have had observed excellent reliability, with 100% of patients ventilated at the correct tidal volume, increased from a baseline of 0%. We have attributed this success to the willingness of the staff to adopt an easy to use technique with high reliability.
We feel that the excellent reliability of our techniques outweighs the reports from O’Brien et al. that our technique may slightly underestimate the tidal volume. Furthermore, since the outcomes for ARDS risk patients is poorer if they are ventilated at >6 mL/kg, 2 a very slight underestimation is not necessarily detrimental provided target blood gas measurements are achieved.